Systems and methods for supercritical water reformation of fuels and generation of hydrogen using supercritical water

ABSTRACT

A system for reforming diesel fuel into hydrogen including feeds for water and diesel fuel, a supercritical water (SCW) reactor in fluid communication with the water feed and the diesel fuel, at least one pre-heater in thermal communication with the water feed, the diesel fuel feed that is configured to heat water from the water feed and diesel fuel from the diesel fuel feed to a predetermined temperature equal to or greater than the critical temperature of water before the water and the diesel fuel are mixed, a water-gas shift (WGS) reactor, and a hydrogen capturing system, where the SCW reactor reforms the diesel fuel into a synthesis gas comprising a mixture of hydrogen and carbon monoxide and outputs the synthesis gas, the synthesis gas output by the SCW reactor is fed into the WGS reactor which converts the carbon monoxide into carbon dioxide and hydrogen and outputs an output gas including a higher percentage of hydrogen to carbon monoxide compared to the synthesis gas, and the hydrogen in the output gas is captured by the hydrogen capturing system.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of United States Non Provisionalapplication Ser. No. 10/723,543 filed on Nov. 26, 2003, presently U.S.Pat. No. 8,038,743, which claims priority to U.S. provisionalapplication Ser. Nos. 60/429,768 filed Nov. 27, 2002 and 60/468,339filed May 6, 2003. The entire disclosure of all of these documents isherein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This disclosure relates to the field of hydrocarbon reformation. Inparticular to the use of supercritical water to reform diesel fuel andto use supercritical water to obtain hydrogen.

2. Description of the Related Art

There is a desire in America and around the world to utilize so calledclean power sources. One of the technologies that has been making aparticular impression in clean power is the so-called “fuel cell” whichproduces electricity by the electrochemical reaction of an oxidizer anda fuel (generally hydrogen gas). While the process is similar in manyways to a battery, fuel cells have the advantage that they do not rundown or require recharging, so long as there is fuel and oxidant, thereis electricity.

The operation of a fuel cell is relatively straight forward. Protonsflow from the fuel electrode (anode) through an ion-conducting membraneto an oxidant electrode (cathode) and combine with oxygen to form water.The electrons in turn flow from the anode to the cathode, through anexternal electric circuit, to create electricity. As the electricity iscreated through the chemical combination, there is no combustion and,therefore, the associated by-products of combustion are eliminated.

Fuel cells have drawn particular interest in automobile and vehiclepower, but are useable for any type of technology where electricity canbe used as power. In particular, the fuel cell may replace conventionalchemical batteries or even conventional electric power plants. The fuelcell is of particular interest because it can operate at efficienciestwo to three times that of the internal combustion engine, and itrequires no moving parts. Further, the fuel cell operates “clean” sincethe only outputs of its process (presuming hydrogen is used as fuel) areheat, electricity, and water.

The biggest hurdle to the fuel cell concept, particularly in vehicleuse, is to obtain hydrogen in sufficient quantities and at reasonablecost to make the fuel cell economically competitive. Further, in orderto switch vehicles to fuel cell power, it is necessary for there to beinfrastructure to distribute hydrogen to provide the hydrogen fuel tothe fuel cells. Because of the lack of infrastructure to distributehydrogen to consumers, especially when compared to existinginfrastructure to distribute fossil fuels, many of the proposals forhydrogen generation reform existing automobile fuels into hydrogen.Further, other consumers, such as the military, are interested in beingable to obtain hydrogen as fuel at remote locations. Many of theseconsumers also already rely on internal combustion engine power sourcesand already have extensive infrastructure and support structurededicated to distributing fossil fuels.

Reforming is preferable because it allows for existing fossil fueldistribution infrastructure to be converted over time to a hydrogendistribution infrastructure, without inconvenience to first adopters ofhydrogen technology, by allowing hydrogen to be obtained at conventionalsources where fossil fuels are already available. Because of the needfor infrastructure to be available to lead to technology adoption, sometechnologies for producing hydrogen simply require too specialized ofmaterials and transportation infrastructure to be utilized efficientlyat this time.

Reforming technologies allow for hydrogen to be generated wherever thereare already fossil fuel sources present by reforming the fossil fuelinto hydrogen. For instance, hydrogen may be formed at the refinery anddistributed, or, if the reformer equipment is sufficiently small, areformer may be placed at a conventional service station to reformautomobile fuels into hydrogen on demand. If the reformer is smallenough, it may even be used on-board an automobile.

Some of the most well known types of fuel reforming systems are steamreforming, partial oxidation and Autothermal reforming (ATR) (which isessentially a process using both steam reforming and partial oxidationtogether to eliminate inefficiencies). The problems with ATR reformersare that they require a very high temperature (850° C. or higher) and anexpensive catalyst such as platinum or nickel to be effective. Further,the catalyst reactivity normally drops very rapidly as the processcontinues due to poisoning of the catalyst through impurities (such assulfurous compounds or carbonyls) formed in the process unless expensivefuel prefiltering processes are used. Therefore, ATR technologies may beimpracticable for use without significant safety, filtering, and powerrequirements. These requirements can, in turn, render the technologyineffective for use with existing fossil fuel infrastructure.

SUMMARY OF THE INVENTION

Because of these and other problems in the art, described herein aresystems and methods for using supercritical water in a process forconverting hydrocarbon fuels, such as, but not limited to, diesel andother automotive, marine, or aircraft fuels into hydrogen. Further,there is described herein systems for using supercritical water togenerate hydrogen, principally for use as a fuel in fuel cells, fromhydrocarbons.

Described herein, in an embodiment is a method for generating hydrogenfrom a hydrocarbon comprising: having a supercritical water reformer(SCWR); providing the SCWR both supercritical water and at least onehydrocarbon; using supercritical water to reform the hydrocarbon intohydrogen; and capturing the hydrogen.\

One embodiment includes a system for reforming diesel fuel into hydrogencomprising feeds for water and diesel fuel, a supercritical water (SCW)reactor in fluid communication with the water feed and the diesel fuelat least one pre-heater in thermal communication with the water feed andthe diesel fuel feed that is configured to heat water from the waterfeed and diesel fuel from the diesel fuel feed to a predeterminedtemperature equal to or greater than the critical temperature of waterbefore the water and the diesel fuel are mixed in the SCW, a water-gasshift (WGS) reactor and a hydrogen capturing system where the SCWreactor reforms the diesel fuel into a synthesis gas comprising amixture of hydrogen and carbon monoxide and outputs the synthesis gas,the synthesis gas output by the SCW reactor is fed into the WGS reactorwhich converts the carbon monoxide into carbon dioxide and hydrogen andoutputs an output gas including a higher percentage of hydrogen tocarbon monoxide compared to the synthesis gas, and the hydrogen in theoutput gas is captured by the hydrogen capturing system.

In another embodiment, the capturing system captures the hydrogen in achemical hydride. In another embodiment, the chemical hydride is sodiumhydride. In another embodiment, the chemical hydride is boron hydride.In another embodiment, oxygen is fed into the SCW reactor in conjunctionwith the diesel fuel and the water.

In another embodiment, the oxygen is fed as a component of air. Inanother embodiment, the system includes a sensor and control system formonitoring at least one of the synthesis gas and the output gas andadjusting the feeds based on the sensing.

In another embodiment, the sensor and control system comprises a gaschromatograph.

Another embodiment includes a system for generating hydrogen fromhydrocarbons comprising a preheating unit that preheats the diesel fueland water to a temperature equal to or greater than the criticaltemperature of water before the water and the diesel fuel are mixed, asynthesis gas obtaining unit that obtains a synthesis gas comprising amixture of hydrogen and carbon monoxide from a mixture of the preheateddiesel fuel, the preheated water, and air, a hydrogen increasing unitthat increases the percentage of hydrogen in the synthesis gas, and ahydrogen capturing unit that captures the hydrogen in a form useful asfuel for a fuel cell.

Another embodiment includes a system for reforming jet fuel intohydrogen comprising feeds for water and the jet fuel, a supercriticalwater (SCW) reactor in fluid communication with the water feed and thejet fuel, at least one pump in fluid communication with the jet fuelfeed and configured to pressurize the jet fuel feed to a predeterminedpressure at or greater than the critical pressure of water, at least onepre-heater in thermal communication with the water feed and the jet fuelthat is configured to heat water from the water feed and jet fuel fromthe jet fuel feed to a predetermined temperature equal to or greaterthan the critical temperature of water before the water and the jet fuelare mixed in the SCW reactor, a water-gas shift (WGS) reactor, and ahydrogen capturing system, where the SCW reactor reforms the diesel fuelinto a synthesis gas comprising a mixture of hydrogen and carbonmonoxide and outputs the synthesis gas, the synthesis gas output by theSCW reactor is fed into the WGS reactor which converts the carbonmonoxide into carbon dioxide and hydrogen and outputs an output gasincluding a higher percentage of hydrogen to carbon monoxide compared tothe synthesis gas, and the hydrogen in the output gas is captured by thehydrogen capturing system.

In another embodiment, the jet fuel is JP-8 fuel. In another embodiment,the capturing system captures the hydrogen in a chemical hydride. Inanother embodiment, the chemical hydride is sodium hydride. In anotherembodiment, the chemical hydride is boron hydride. In anotherembodiment, oxygen is fed into the SCW reactor in conjunction with thediesel fuel and the water. In another embodiment, the oxygen is fed as acomponent of air.

In another embodiment, the system includes a sensor and control systemfor monitoring at least one of the synthesis gas and the output gas andadjusting the feeds based on the sensing. In another embodiment, thesensor and control system comprises a gas chromatograph.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows an embodiment of a supercritical water reformer (SCWR) foruse to reform diesel fuel into hydrogen.

FIG. 2 shows a graph indicating the states of water and showing thesupercritical state.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

Disclosed herein, among other things, is a supercritical water reformer(SCWR) for use in converting fuels into hydrogen. The operation of theSCWR utilizes a supercritical water (SCW) reactor in conjunction withother hydrogen harvesting and generation apparatus to produce a portablehydrogen generation system for use to generate hydrogen fromhydrocarbons including hydrocarbon fuels.

The terms “fuels” or “hydrocarbon fuels” as used herein is intended tobe a general term relating to liquid hydrocarbons generally used as fuelin motor vehicles, generators, or other internal combustion enginepowered devices. However, fuels include all liquid hydrocarbonsgenerally of the chemical formula C₆1-1₆, where n and m may be anyvalue. This specifically includes, but is not limited to hydrocarbonsclassified as paraffins (CnH2n+2), naphthenes (C₆H2₆), olefins (C6H2n),and aromatics (CnH2n-6). Fuel is also occasionally used to refer to theuse of hydrogen as fuel for a fuel cell, but such use is clearlyindicated where it occurs.

Fuels also specifically include, but are not limited to, gasoline,diesel fuel and jet fuel, as well as fuel additives, biomass fuels, oralternative fuels used for motor vehicles or internal combustion enginessuch as ethanol or biodiesel. Generally, fuels will comprise a mixtureof hydrocarbons (particularly with chemical formulas between andincluding C6H14 and C22H46). Some more prevalent hydrocarbons present infuel are methane (CH4), propane (C3118), ethane (C2H6), octane (C8H₁8)and dodecane (C12H26). The discussion below will presume the exemplaryfuel used is classified as “diesel fuel” by the refining industry toillustrate a preferred embodiment. Generally, diesel fuel refers to fuelhaving most carbon numbers between 10 and 22. This exemplary embodiment,however, should not be taken as limiting as one of ordinary skill in theart would understand how the process can be applied to any fuel,hydrocarbon, or combination of hydrocarbons.

Further, while hydrocarbon fuels are the preferred fuel for the SCWR toconvert to hydrogen, one of ordinary skill in the art would understandthat and SCWR can reform other hydrocarbons and biomass fuels intohydrogen gas. Therefore in an embodiment of the invention, the fuelsused may be any hydrocarbon of the form C_(i),H_(m).

FIG. 1 provides an embodiment of a block diagram showing the layout of asupercritical water reformer (SCWR) (50) which can reform diesel fuelinto lighter hydrocarbons such as methane, ethylene, and ethane, andultimately into synthesis gas, i.e., carbon monoxide (CO) and hydrogen(H2). In FIG. 1 there are generally four broad component stages whichrelate to the operation of the SCWR (50).

In the stage one components (100) diesel fuel and a supercriticalwater/air mixture is prepared. In the stage two components (200), asupercritical water (SCW) reactor (201) reforms the diesel fuel, water,and air mixture into a synthesis gas comprising a mixture of hydrogen,carbon dioxide (CO2), and carbon monoxide (CO). This synthesis gas isthen carried in a feed stream (215) with other compounds such as sulfurdioxide (SO2), nitrogen (N2), oxygen (O2), and water (H2O). In the stagethree components (300) a purification reactor such as a forwardwater-gas shift (WGS) reactor (301) is used to reduce carbon monoxidecontent and increase hydrogen content in the synthesis gas. In the stagefour components (400), the hydrogen is captured into an easilytransportable and storable form such as a chemical hydride. Othermaterials are either discarded or recycled back into the SCWR (50).

In the stage one components (100) there are three chemical feeds: airfeed (101), water feed (103) and diesel fuel feed (105). The air feed(101) is generally arranged so as to allow air to be obtained from apressurized air tank or from simply pumping in atmospheric air. In apreferred embodiment, the percentage of air in the resultant mixturewill be of significantly smaller amounts than the other two ingredientsor may be eliminated in an alternative embodiment. In a preferredembodiment air comprises from 1-10% by moles of water fed and at thesame time 0-50% by moles of diesel fuel. Mass flow controller (121)controls the amount of air mass flowing in air feed (101). The air fedby air feed (101) will generally comprise a mixture of nitrogen, oxygenand various other gases. Generally the nitrogen will comprise about 78%of the mixture, oxygen about 21% of the mixture and the other gasescomprising 1%. For the purpose of this disclosure, the exact compositionof the other gases will be ignored as their effect is relatively minimalon the resulting reaction. In an alternative embodiment, the air feed(101) may actually feed pure oxygen into the system as the air feed(101) is principally used to feed oxygen. The nitrogen is generallypresent but not utilized.

Each of the water feed (103) and diesel fuel feed (105) are liquid pumpsdesigned to feed water or diesel fuel into the system using any type ofliquid feed technology known now or later developed. The pumpspreferably pressurize the water and diesel fuel to a pressure level ator above the critical pressure of water (218 atm) shown in FIG. 2. Thewater feed (103) in the depicted embodiment utilizes an enclosed cyclewhere the water fed by the water feed (103) is water removed from theinput or resultant output of the WGS reactor (301). This type ofself-contained system is preferable as it allows for more efficient useof water in the SCWR (50). Before the water and diesel fuel are mixed inSCW reactor (201), they will generally pass through preheaters (107)where they are heated to a level approaching or possibly passing thecritical temperature of water (374° C.) as shown in FIG. 2. The air andsupercritical water are preferably mixed prior to entering SCW reactor(201). The preheating step places a lower requirement on the SCW reactor(201) to heat the mixture which can result in an SCWR which can producehydrogen faster upon activation. Generally, there will be valves (111)between the air feed (101), diesel fuel feed (105), water feed (103),and the SCW reactor (201) to prevent back feed, to regulate the amountof each material provided to the resultant input mixture, and tomaintain the pressure inside the SCW reactor (201).

As the input mixture of supercritical water and air, and the diesel fuelenters the second stage components (200) they both enter into the SCWreactor (201). The SCW reactor (201) is typically a vessel constructedaccording to known high pressure design codes of Hastelloy—C276 orInconel. In a preferred embodiment, the SCW reactor (201) constructionmaterial includes nickel which has a mild catalytic effect on thereforming reaction. While the catalytic effect is a bonus, poisoning (asdiscussed later) is generally avoided due to the extractive nature ofsupercritical water. In an alternative embodiment, the reactor may beconstructed of stainless steel. The SCW reactor (201) may be either amixed-type or continuous tubular type. As depicted in FIG. 1, the SCWreactor (201) is equipped with heating elements (223). As thesupercritical reforming reaction is exothermic, the energy requirementsof the SCW reactor (201) may be, in an embodiment, self-sustaining.

In the SCW reactor (201), the supercritical water drives the chemicalreformation of the fuel into hydrogen, carbon monoxide, carbon dioxide,and water. The SCW reactor (20.1) performs this reforming through theproperties of supercritical water. In particular: supercritical watercompletely dissolves both diesel fuel and oxygen, thus establishing ahomogeneous reaction phase without need to raise the temperatureexcessively as was required in ATR reforming. Further, due to theintimacy (or close proximity) between reactant molecules insupercritical water, there is no need for a heterogeneous catalyst toperform the reforming. Instead, only the two components of fuel andwater are required acting as both the components of the reaction and thecause of the reaction. Generally, the reforming in SCW reactor (201)will occur according to the following chemical relation:C,,H,,,+nH₂O=nCO+(n+Vgn)H₂  Equation 1

Where n and in are used generally to represent any hydrocarbon beingreformed. Further, Equation 1 may show slight variation if particularhydrocarbons are being used which have a slightly different structure.Equation 1 simply provides the stoichiometric requirements that in theinteraction the number of water moles present needs to match the numberof carbon moles in the hydrocarbon. The exact numbers for diesel fuelare determined experimentally and will depend on particular fuelformulations. Further, in operation as the water acts as both reactantand reaction medium there will generally be a significant excess ofwater provided to the SCW reactor relative to Equation 1 to meet processrequirements.

In the embodiment of FIG. 1, a very small amount of oxygen (preferably0-2% by moles of water feed and 0-10% by moles of diesel fuel) isintroduced into the reaction to accelerate the reforming by combiningwith some of the carbon in the diesel fuel to form additional carbonmonoxide or carbon dioxide. Further, the introduction of small amountsof oxygen (air) can help with carbon-carbon bond cleavage and canprovide a seed amount of carbon monoxide molecules to the system. Thisoxygen is generally introduced as a component of air from air feed(101). In an alternative embodiment, oxygen (air) need not be included.Typically, however, this alternative embodiment will require highertemperature.

In the depicted embodiment, the SCW reactor (201) is monitored by atemperature controller (221) which senses the internal temperature ofthe SCW reactor (201) using temperature transducer (222), and asnecessary applies additional heat input to the SCW reactor (201) usingheating elements (223) to maintain the temperature in the SCW reactor(201) is at or above the critical temperature of water. The pressureinside the SCW reactor (201) is preferably monitored by pressuretransducer (235), and as necessary the pressure of water feed (103) anddiesel fuel feed (105) is adjusted to maintain the pressure in the SCWreactor (201) at or above the critical pressure of water. Pressurerelief valve (231) also monitors the pressure inside the SCW reactor(201) to detect pressure reaching dangerous levels, if such high levelsare detected, pressure will be released from SCW reactor (201) via vent(233).

Generally, the SCW reactor (201) will also output sulfurous compounds(such as sulfur dioxide (SO2) or hydrogen sulfide (112S)) frominteraction with sulfur impurities in the fuel (as Equation 1 presumespure hydrocarbons which hydrocarbon fuels rarely are). These sulfurouscompounds can foul ATR reactors or other types of reformers but havelittle effect on the SCW reactor (201). Further, as the air fed by airfeed (101) generally includes a non-trivial amount of nitrogen this willalso be output. Under supercritical water conditions, nitrogen generallydoes not react with oxygen so nitrogen oxides (NOx) are not formed. Thetemperature is too low for such formation. Therefore, nitrogen simplypasses through the SCW reactor (201).

Once the SCW reactor (201) has reformed the diesel fuel and water intothe synthesis gas of Equation 1, the resultant feed stream (215)(including the synthesis gas) is passed through a pressure regulatingvalve (211) and into a molecular sieve (203). Valve (211) also serves tohelp maintain the pressure inside SCW reactor (201). The molecular sieve(203) is a device designed to trap molecules of certain types. In thiscase, the molecular sieve (203) principally serves to capture anysulfurous compounds (particularly sulfur dioxide) and carbonyl compoundscreated in or passed through the SCW reactor (201). The sieving canoccur using any technology known to those of ordinary skill in the artsuch as, but not limited to, absorptive materials or materials havinglimited pore size to prevent passage of molecules above that particularpore size. This removal is desirable because the sulfurous compounds cangenerally not be further refined to produce additional hydrogen and canaffect the effectiveness of the stage three components (300). Therefore,they are preferably removed at this stage and discarded. In anotherembodiment, the molecular sieve (203) is used in conjunction with activecarbon beds placed in series. This combination is particularly effectivein small scale systems.

Since there are no noble metal or other heterogeneous catalysts involvedin the fuel reforming reaction (Equation 1) as can be seen above, theprocess efficiency is not affected by the presence of the sulfurouscompounds (such as sulfur dioxide or hydrogen sulfide) or carbonyls(iron penta-carbonyl or nickel carbonyls) in the stage two components(200). Therefore, expensive sulfur pre-cleanup stages required for otherreforming techniques can be eliminated. Further, carbon soots are notformed in the SCW reactor (201) which does not require their eliminationor cleanup.

The stage three components (300) are principally related to increasinghydrogen content in the feed stream (215) output by the SCW reactor(201′). In particular, the feed stream (215) output by the SCW reactor(201) contains nontrivial amounts of carbon monoxide (CO) (as shown inEquation 1). The beneficial conversion of carbon monoxide (CO) intohydrogen (H2) becomes a desirable step. This type of conversion is knownand may be performed using a forward water-gas shill (WGS) reactor (301)which operates generally according to Equation 2:CO+H₂O═CO₂+H₂  Equation 2

The water required for the reaction may be water from the stage two(200) components. In an alternative embodiment, additional water may beadded to the feed stream (215) at the WGS reactor (301) if needed orexcess water vapor may be removed from the feed stream (215). Inparticular, the water collector (306) may provide water from priorreactions back to the WGS reactor (301) to provide the necessary waterif needed. However, generally to make the WGS reactor (301) operate inthe forward direction to increase available hydrogen (as opposed toincreasing carbon monoxide), water will be removed from the feed stream(215) prior to the WGS reactor (301). The flow of feed stream (215) intoWGS reactor (301) is preferably controlled by mass flow controller (321)as shown in FIG. 1.

The WGS reaction will generally be carried out over a metal oxidecatalyst such as zinc oxide on an aluminum support (Z,,0/Al203) ataround 200° C. As is known to those of ordinary skill in the art, theWGS reaction equilibrium can be easily reversed by changing thecompositions (specifically the carbon monoxide and water or carbonmonoxide and carbon dioxide ratio) of the feed stream (215). In order tomaximize the conversion, therefore, it is generally necessary to reducethe water concentration in the feed stream from the SCW reactor (201)into the WGS reactor (301). Further, because of the reversibility of thereaction, there will generally still be some carbon monoxide (generallyaround 0.5-1 percent) remaining in the output stream (315) of the WGSreactor (301). Further, the WGS reactor (301) enriches the hydrogenconcentration while reducing the carbon monoxide concentration byEquation 2, the concentration of carbon dioxide also increased in theoutput stream (315) of the WGS reactor (301) compared to feed stream(215).

It should be clear at this stage that the WGS reactor (301) is thereforereleasing an output stream (315) of different chemical species includingsynthesis gas components, carbon monoxide, carbon dioxide, and hydrogen.Further the output stream (315) may include nitrogen, water, and oxygenas well as other trace gases left over from inputs and incompletereactions. As the output stream (315) is prepared to enter the stagefour components (400), the temperature will now generally be furtherlowered to allow precipitation of the water out of its gaseous stage.This precipitation may be performed by a condenser (305). The resultantliquid water is collected by water collector (306) and fed back throughvalve (311) to water feed (103) for reuse as shown in the embodiment ofFIG. 1. In an alternative embodiment, the liquid water may be recycledback to WGS reactor (301) or may be removed from the SCWR (50) anddiscarded.

The stage four components (400) capture and store hydrogen and recyclethe other components back into other stage components of the SCWR (50)for reuse or further purification. Water which needs to be removed priorto the WGS reactor (301) can also be cycled back around to the waterfeed (103). Generally, the SCWR (50) will require no water input as thatrecycled is the same as that originally used. However, in an alternativeembodiment, water may be added or removed from the SCWR (50) at waterfeed (103) or at any other point.

Hydrogen may be captured by any method known to those of ordinary skillin the art to capture hydrogen, but is preferably captured by using acapturing system (405) where the remaining output stream (413) ofcondenser (305) is passed over a metal or compound such as boron (borax)or sodium to form a chemical hydride such as boron hydride or sodiumhydride. Metal alloys including titanium, manganese, nickel, andchromium, as well as alkali earth metals, may alternatively be used asstorage media. In a still further embodiment carbon nanotubes may beused to capture hydrogen in the capturing system (405). When using achemical hydride, particularly a metal hydride, hydrogen can be capturedin a simple reaction even under a low-temperature/pressure environment.Further, the release of hydrogen is convenient as it merely requirescontacting the hydride with water and capturing the resulting gas. Theselectivity of metal hydride capture is also good compared to unintendedcapture of other gases provided in the remaining output stream (413)resulting a relatively high capture of hydrogen and relatively lowcapture of any other gases.

After hydrogen capture, carbon dioxide may be removed from the system asit is not particularly useful to recycle. To perform this removal, acidgas removal (AGR) reactor (407) may be placed in the resultant gasstream (415). The AGR reactor (407) may utilize polyethylene glycoldimethyl ethers or other components suitable for absorbing carbondioxide to remove the carbon dioxide from the resultant gas stream(415). Once the carbon dioxide has been removed from the process itshould be clear that the remaining gas stream (515) is now only leftwith carbon monoxide and the residual nitrogen and oxygen. Thesecomponents can then be returned to the WGS reactor (301) to attempt toobtain hydrogen from the remaining carbon monoxide. Nitrogen and oxygenmay be bled off or otherwise removed if necessary or may simply becycled.

Control of the SCWR (50) is performed in the embodiment of FIG. 1 bymonitoring the SCW reactor (201) output stream (feed stream (215)) andthe WGS reactor (301) output stream (315). A sensor and control system(307) containing a gas chromatograph or other suitable gas sensordetermines the hydrogen content in feed stream (215) and in outputstream (315), and adjusts the air feed (101), water feed (103), anddiesel fuel feed (105) to control the amount of inputs into the SCWreactor (201). The sensor and control system (307) may control air feedinput into the SCW reactor (201) by means of mass flow controller (121).The sensor and control system (307) further may control input into theWGS reactor (301) by means of mass flow controller (321). The sensor andcontrol system (307) may be manually regulated or may automaticallyregulate the process such as by use of a digital processor. Alternativeembodiments of SCWR (50) may include energy recovery means such as heatexchangers to reclaim heat from the output of the SCW reactor (201) touse to pre-heat water feed (103) and diesel fuel feed (105), andpressure or work exchangers to reclaim pressure from the output of SCWreactor (201) to pressurize water feed (103), diesel fuel feed (105),the water and fuel feeds into the SCW reactor (201).

The embodiment of FIG. 1 does not require a particularly large setup, orparticularly complicated operation. Compared to ATR systems, the SCWR(50) operates at a relatively low temperature. Further, because theprocess operates in a condensed phase, particularly under the highpressure of the SCW reactor (201), the SCWR (50) size can besubstantially smaller than an ATR reactor. It is seen that the SCWR (50)could be assembled to be readily vehicle portable to a variety oflocations. In particular, the SCWR (50) would be able to fit on a palletsuch as a forklift pallet or a 463L pallet as used by the United StatesAir Force. Alternatively, a scaled up version of the SCWR (50) could beplaced in an over-the-road (OTR) truck trailer or on a pallet, crop, orflatrack utilized by Load Handling System (LHS) trucks such as theHEMTT-LHS truck used by the United States Army.

Because of the relatively low temperature operation, the relativelysimple hydrogen capture, and the portable size of the SCWR (50), theSCWR (50) is suitable for use in a variety of locations to provide aready source of hydrogen, such as to power fuel cell vehicles,generators, or other devices. In particular, the SCWR (50) may be placedat an existing service station where it can obtain hydrocarbon fuel fromthe existing service station's tanks which it reforms into hydrogen toprovide to fuel cell vehicles. In the military context, the SCWR (50)can be transported to a site where diesel fuel is provided (such as anexisting fuel dump or similar site) and can then reform the diesel fuelto hydrogen to allow the use of military fuel cell technology withouthaving to overhaul military infrastructure to provide for hydrogentransportation.

While the invention has been disclosed in connection with certainpreferred embodiments, this should not be taken as a limitation to allof the provided details. Modifications and variations of the describedembodiments may be made without departing from the spirit and scope ofthe invention, and other embodiments should be understood to beencompassed in the present disclosure as would be understood by those ofordinary skill in the art.

What is claimed:
 1. A system for reforming diesel fuel into hydrogencomprising: feeds for water and diesel fuel; a supercritical water (SCW)reactor in fluid communication with the water feed and the diesel fuel;at least one pre-heater in thermal communication with the water feed andthe diesel fuel feed that is configured to heat water from the waterfeed and diesel fuel from the diesel fuel feed to a predeterminedtemperature equal to or greater than the critical temperature of waterbefore the water and the diesel fuel are mixed in the SCW; a water-gasshift (WGS) reactor; and a hydrogen capturing system; wherein, the SCWreactor reforms the diesel fuel into a synthesis gas comprising amixture of hydrogen and carbon monoxide and outputs the synthesis gas;the synthesis gas output by the SCW reactor is fed into the WGS reactorwhich converts the carbon monoxide into carbon dioxide and hydrogen andoutputs an output gas including a higher percentage of hydrogen tocarbon monoxide compared to the synthesis gas, and the hydrogen in theoutput gas is captured by the hydrogen capturing system.
 2. The systemof claim 1 wherein the capturing system captures the hydrogen in achemical hydride.
 3. The system of claim 2 wherein the chemical hydrideis sodium hydride.
 4. The system of claim 3 wherein the chemical hydrideis boron hydride.
 5. The system of claim 1 wherein oxygen is fed intothe SCW reactor in conjunction with the diesel fuel and the water. 6.The system of claim 5 wherein the oxygen is fed as a component of air.7. The system of claim 1 further comprising a sensor and control systemfor monitoring at least one of the synthesis gas and the output gas. 8.The system of claim 7 wherein the sensor and control system comprises agas chromatograph.
 9. A system for generating hydrogen from hydrocarbonscomprising: a preheating unit that preheats the diesel fuel and water toa temperature equal to or greater than the critical temperature of waterbefore the water and the diesel fuel are mixed; a synthesis gasobtaining unit that obtains a synthesis gas comprising a mixture ofhydrogen and carbon monoxide from a mixture of the preheated dieselfuel, the preheated water, and air; a hydrogen increasing unit thatincreases the percentage of hydrogen in the synthesis gas; and ahydrogen capturing unit that captures the hydrogen in a form useful asfuel for a fuel cell.
 10. A system for reforming jet fuel into hydrogencomprising: feeds for water and the jet fuel; a supercritical water(SCW) reactor in fluid communication with the water feed and the jetfuel; at least one pump in fluid communication with the jet fuel feedand configured to pressurize the jet fuel feed to a predeterminedpressure at or greater than the critical pressure of water; at least onepre-heater in thermal communication with the water feed and the jet fuelthat is configured to heat water from the water feed and jet fuel fromthe jet fuel feed to a predetermined temperature equal to or greaterthan the critical temperature of water before the water and the jet fuelare mixed in the SCW reactor; a water-gas shift (WGS) reactor; and ahydrogen capturing system; wherein, the SCW reactor reforms the dieselfuel into a synthesis gas comprising a mixture of hydrogen and carbonmonoxide and outputs the synthesis gas, the synthesis gas output by theSCW reactor is fed into the WGS reactor which converts the carbonmonoxide into carbon dioxide and hydrogen and outputs an output gasincluding a higher percentage of hydrogen to carbon monoxide compared tothe synthesis gas, and the hydrogen in the output gas is captured by thehydrogen capturing system.
 11. The system of claim 10 wherein the jetfuel is JP-8 fuel.
 12. The system of claim 10 wherein the capturingsystem captures the hydrogen in a chemical hydride.
 13. The system ofclaim 12 wherein the chemical hydride is sodium hydride.
 14. The systemof claim 12 wherein the chemical hydride is boron hydride.
 15. Thesystem of claim 10 wherein oxygen is fed into the SCW reactor inconjunction with the diesel fuel and the water.
 16. The system of claim15 wherein the oxygen is fed as a component of air.
 17. The system ofclaim 10 further comprising a sensor and control system for monitoringat least one of the synthesis gas and the output gas and adjusting thefeeds based on the sensing.
 18. The system of claim 17 wherein thesensor and control system comprises a gas chromatograph.